Issue with stale resolv.conf state
Florian Weimer
fweimer@redhat.com
Mon Mar 11 10:51:19 GMT 2024
* John Levon:
> I don't understand the first part of the comment, but indeed, ->resp doesn't
> match. In particular:
>
> 62 return ctx->resp->options == ctx->conf->options
>
> and ctx->resp (aka _resp) has 0x47002c1 whereas ctx->conf has 0x41002c1.
>
> I'm not sure but I suspect the additional RES_SNGLKUP|RES_SNGLKUPREOP
> may be due to this code:
>
> 1000 /* There are quite a few broken name servers out
> 1001 there which don't handle two outstanding
> 1002 requests from the same source. There are also
> 1003 broken firewall settings. If we time out after
> 1004 having received one answer switch to the mode
> 1005 where we send the second request only once we
> 1006 have received the first answer. */
> 1007 if (!single_request)
> 1008 {
> 1009 statp->options |= RES_SNGLKUP;
> 1010 single_request = true;
> 1011 *gotsomewhere = save_gotsomewhere;
> 1012 goto retry;
> 1013 }
> 1014 else if (!single_request_reopen)
> 1015 {
> 1016 statp->options |= RES_SNGLKUPREOP;
> 1017 single_request_reopen = true;
> 1018 *gotsomewhere = save_gotsomewhere;
> 1019 __res_iclose (statp, false);
> 1020 goto retry_reopen;
> 1021 }
That's a very good point. Yes, the current reloading code does not take
into account that we change _res.options dynamically based on network
behavior.
That automatic configuration change based on temporary network glitches
is problematic in other contexts as well (it may further trigger bugs in
dual query processing).
Maybe we should just remove the automatic downgrade, basically not
persist this across queries anymore.
Thanks,
Florian
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